The present invention concerns a regulating drafting system, in particular but not exclusively, for application at a card machine delivery arrangement. The present invention furthermore concerns a card with a first sensor for scanning the mass of the fibre material delivered by the card, in particular of the card sliver, the signal transmitted by the sensor being used for regulating the drive of the supply device of the card and preceded by a sliver storage device.
It is known that cards can be provided with regulating drafting systems in order to improve, or to ensure respectively, the evenness of the sliver delivered by the card. The following documents are cited merely as examples of the numerous publications representing the state of the art concerning this subject:
DE-A-1921248 Zellweger
DE-A-2912576 Zellweger
US-B-4075739 Rieter
EP-C-275471 Rieter
The solutions according to the sate of the art permit xe2x80x9cmaintaining of the sliver weightxe2x80x9d (Long term regulation) as well as the elimination of the influence of variable lap layer thickness at the intake (short term disturbances).
Regulating drafting systems arranged at the card delivery are known from the following publications:
JP-Gbm-56017/78 Nihon Keikizai KK
JP-A-155231/77 Nagoya Kinzoku Harinuno KK
DE-A-1931929 Zinser
DE-A-2230069 Texcontrol
CH-B-599993 Graf
EP-C-354653 Hollingsworth
EP-A-544425 Hollingsworth
EP-A-6041137 Hollingsworth
EP-A-617149 Grossenheiner Textilmaschinenbau GmbH
EP-A-643160 Howa Machinery, Ltd.
EP-A-692560 Chemnitzer Spinnereimaschinenbau GmbH
US-B-5400476 Myrick-White, Inc.
The card operates at a constant (pre-settable) production speed; i.e. the fibre sliver is delivered at a pre-determined speed from the delivery arrangement. The function of a regulating drafting system implies that the draft be variable (controllable). Provision of a large sliver storage device between the card and the drafting system intake is undesirable. Thus the delivery speed of the drafting system must be variable. This, however, creates problems concerning the drive of the sliver deposition or coiler system, the inertia of which is relatively considerable, arranged downstream from the drafting system.
Various devices are known, e.g. from the DE-OS-19 19 929, in which a sliver storage device is arranged between the card and a regulating drafting system. This can be seen in particular from the FIGS. 3 and 4 of the DE-OS reference. Adjoining the regulating drafting system, a sliver storage device is arranged driven by a separate motor. The measured values determined by the pair of measuring rolls upstream from the regulating drafting system are compared to the pre-set desired values. The resulting deviation signal serves for controlling the drive motor of the intake pair of rolls of the drafting system in order to adapt the draft ratio, and to level out thin and thick places respectively. At the same time, this signal is transmitted to the control device of the card, or of its main drum respectively, in such a manner that this drive also can be adapted correspondingly. The reaction of the card, however, is subject to substantially higher inertia than the drafting system. The resulting differences in the material delivery speed, and in the material intake speed respectively, are levelled out in the sliver storage device adjoining the card. The storage device in this arrangement is provided with sensors for scanning the contents of the storage device. Based on the contents scanned by the sensors in the sliver storage device, the drives of the fibre sliver source (card) and of the sliver take-up device (coiler) are charged correspondingly in such a manner that the contents of the sliver storage device is maintained substantially constant. This adaptation of the two drives however, results in additional differences, especially as the elements of the card (e.g. the card main drum) are subject to inertia influences differing from the ones in the elements of the sliver depositing device (coiler). Furthermore, in this case exact scanning of the sliver storage device contents must be provided.
Furthermore, from the previously published DE-A1-44 24 490 a co-ordination of cards is known in which a storage device is coordinated to each card downstream and in which the card slivers delivered by the individual storage devices after passing through a drafting system are delivered to a common sliver deposition device or coiler. In order to compensate for the loss of one of the card slivers supplied to the drafting system, the delivery speed of the drafting system is reduced until the missing card sliver has been re-inserted. In this arrangement a scanning sensor is co-ordinated to each individual card sliver. Owing to the reduction in delivery speed, corresponding to the loss of one card sliver, the fibre sliver reserve for the draw frame is exhausted more slowly than in the normal operating mode at higher intake speeds. In the example shown, an increase of the card delivery speed also is proposed if the fibre sliver storage device arranged downstream is depleted to below a pre-determined value in such a manner that the operation of the subsequent draw from is not jeopardized. The arrangement shown is suitable for levelling out massive short term variation (loss of a sliver). Levelling out long term deviations however, is not envisaged using this arrangement, or is solved unsatisfactorily only.
For levelling out long period mass deviations in the fibre sliver delivered by the card it is proposed in DE-A1 29 12 576 that the thickness of the fibre sliver delivered by the card be measured and compared to a pre-set desired value. The signal thus determined is used in controlling the material supply device (feed roll) arranged upstream from the card. Owing to this arrangement long period deviations in the mass of the card sliver delivered can be reacted on. Avoiding and eliminating of short wave deviations e.g. using a regulated drafting system arranged downstream is not envisaged in the arrangement described.
The solutions proposed thus far generally provide the drafting system for levelling out short term variations in the fibre sliver. They correspondingly propose of a measuring sensor at the intake of the drafting system.
Objects and advantages of the present invention will be set forth in the following description, or may be obvious from the description, or may not be learned through practice of the invention.
The present invention in a first aspect provides a card with a regulating drafting system arranged at the card delivery. Measuring values are obtained from the drafted fibre sliver for regulating the drafting system (measuring point at the drafting system delivery). For this purpose the drafting bodies (i.e. the rotatable bodies driven at the higher speed for generating the draft) can be used as sensors. The term xe2x80x9cbodiesxe2x80x9d in this context is understood to comprise such elements such as rolls, (discs), and cylinders.
The drafting bodies can be the delivery elements of the drafting system, in which arrangement the take-in bodies can be driven at a (constant) speed corresponding to the delivery speed of the fibre sliver leaving the card.
The take-in bodies can be coupled to the drive of the card delivery arrangement, or they can be driven under control synchronized with the card delivery arrangement. The take-in arrangement of the drafting system also can be provided with measuring elements, which permits a combination of the arrangement according to the state of the art.
The measuring values used for regulating the draft in the drafting system can be transmitted also to the card regulating device, e.g. for regulating the sliver weight on the card itself. The card preferentially also is equipped with a regulating system which can level out short term weight deviations in the lap fed in.
In cases in which the drafting system delivery speed is variable (for effecting controlled draft adaptations) the sliver deposition arrangement can be driven according to one of the known working principles or according to an equivalent or better solution. The second aspect of the present invention concerns the problems arising in this connection.
The present invention in a second aspect provides a card with a regulating drafting system at the card delivery, in which arrangement for regulating the draft, measuring values are obtained at the intake or at the delivery of the drafting system and the draft is adapted accordingly by changing the delivery speed. In this case the drive of the sliver depositing device (coiler) also is controlled as a function of the measuring values, preferentially in such a manner that the fibre sliver portion between the drafting system delivery and the intake of the sliver depositing device is not subject to an elongation exceeding a certain limit.
The present invention in a third aspect is based on the objective to create a method, and an apparatus respectively, which serves out long term and short term mass deviations in the card sliver delivered by a card, in which arrangement on one hand the rotational speed can be maintained constant and on the other hand storage elements required for balancing out different transporting speeds of the fibre sliver delivered can be kept as small as possible.
This objective is met in that the sensor between the card and the regulating drafting system which is used for regulating the drive of the supply device of the card is arranged between the card and the regulating drafting system and that the base rotational speed of the regulating drafting system is adaptable as a function of the signal transmitted by the sensor.
The base rotational speed is understood to be the rotational speed, or the ratio of the rotational speeds of the individual pairs of rolls of the regulating drafting system which is set for the normal operation of drafting the card sliver supplied. On the basis of this rotational speed, the regulating action is effected by the pair of rolls the rotational speed of which can be regulated in order to level out short wave variations in the fibre mass. As soon as the sensor arranged downstream from the card transmits a signal indicating a long term drift in the fibre mass, the base rotational speed of the regulating drafting system arranged subsequently is changed correspondingly. In this manner, on one hand, timely reaction against such drifting is possible and on the other hand the transporting speed of the fibre sliver supplied to the regulating drafting system can be held on a level not requiring changes in the delivery speed of the card, and the filling level in the fibre sliver storage device can be maintained on an approximately constant level. This signifies that the delivery rotational speed of the card can be kept substantially constant and the capacity of the storage device can be held small.
Furthermore, it is proposed that the sliver storage device be provided with a filling level sensor, the signals of which additionally are used for adapting the base rotational speed of the drafting system. Thus an additional checking control is effected for the buffer zone between the card and the drafting system in order to effect corresponding actions. This sensor in the sliver storage device in this arrangement serves as a supplementary completion and at the same time also for checking the first sensor arranged at the card delivery. The filling level sensor can be laid out with a tolerance spectrum in order to avoid continual increase and decrease of the base rotational speed. This means that the control unit generates a control signal for changing the base rotational speed only in case the signal exceeds the pre-set tolerance zone. In case a disturbance develops in the first sensor downstream from the card, or in case of a break-down of this sensor, the control actions effected on the base rotational speed are initiated by the filling level sensor. During normal operation, the control of the base rotational speed is based on a signal blended from the signals of the first sensor and of the filling level sensor.
Furthermore it is proposed that the rotational speed of the intake rolls of the drafting system can be regulated for levelling out mass deviations detected in the fibre material. In this arrangement a buffer zone between the drafting system and the subsequently arranged sliver depositing device (coiler) can be dispensed with. This signifies that the transport variations possibly occurring in the fibre sliver caused by the regulating action are shifted to the zone upstream from the drafting system.
In this arrangement it is possible, as proposed furthermore, that the delivery rolls of the drafting system be drivingly connected to the drive mechanism of a subsequently arranged sliver deposition device. The drive of the sliver deposition device in this arrangement automatically is adapted as the base rotational speed and is increased or decreased in such a manner that constant relations prevail at all times between the delivery roll of the drafting system and the calender rolls of the sliver depositing device.
For detecting short wave mass deviations in particular, it is proposed that a further sensor be provided for scanning the fibre material delivered by the card, the signals transmitted being used for adapting the regulating device of the drafting system.
Preferentially, the first sensor is arranged between the card and the sliver storage device. In this arrangement, corrective action can be effected early for changing the base rotational speed of the drafting system arranged subsequently in order to maintain the transporting speed of the card sliver supplied to the drafting system approximately constant in spite of the presence of a long term drift in the fibre mass. This means that the fibre sliver buffer present in the sliver storage device arranged upstream can be maintained approximately constant. Using this arrangement the fibre sliver buffer, and the fibre sliver storage device respectively, can be kept small in its capacity.
Furthermore, it is proposed that the further sensor be arranged between the fibre sliver storage device and the regulating drafting system or adjoining the drafting system. In this arrangement this sensor should be arranged as closely as possible near the drafting system in order to keep any time delays between the measuring point and the regulating action as small as possible.
It is also feasible that a device according to the third aspect of the present invention be combined with a device according to the first and/or the second aspect. This will be discussed in the following with reference to the FIG. 6 in more detail.
Embodiments of the present invention are explained in the following in the sense of examples with reference to the illustrated Figures. It is shown in the: